Loud speaker



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c. E. BRIGHAM LOUD SPEAKER Amin Mg w25.

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SEUIL E. BRIGHAM, 0F ,EASTIORANGE NEW JERSEY, ASSIGNOR TO C. BRANDES, ING.;

A 0F NEW YORK, N. Y., A CORPORATION OF N EW YORK.

LOUD SPEAKER.

Application med :rune 14,

' Speaker, of which the following isa specification.

My invention relates broadly to electromagnetic sound reproducersand more pan ticularly to a loud speaker designed particularly for the efficient reproduction of frequencies within the range. employed in radio broadcast reception.

.One of the objects of my invention is to provide a loudspeaker construction wherein the mechanical inertia of the moving parts of the reproducer is substantially eliminated.

' Another object of my invention is to provide a loudspeaker construction cmploying a true floatingv armature eliminating mefulcrum pointsl and pivoted mountings usually employed to support the armature.

Still another object of my invention is to provide an arrangement of permanent magnet structure and an electromagnetic structure having a hollow core `with opposite pole at opposite ends thereof with a freely floating armature mounted within the hollow core and connected with a diaphragm converting electrical energy into sound vibrations.-

A further object of my invention is to provide an assembly of permanent magnet structure and an electromagnetic structure adjacent al casing enclosing a sound reproducing diaphragm. The permanent magnet structure-having pole pieces projectin toward eaich other with flat overlapping aces. The electromagnet structure being disposed between the inwardlyprojecting pole pieces and having a hollow core witha freely floatying armature within the hollow core and between the overlapping pole pieces, the armature being connected with the sound reproducing diaphragm.

M invention will be more clearly underby reference to the accompanying drawings, in which:

Figure l, is a cross sectional view through the loud speaker construction of my inven-l tion; F ig. 2 is a plan view looking beneath the loud speaker construction illustrated ins 1924. Serial No. 720,087.

Fig. l; and Fig. 3 is a side view of the electromagnetic sound reproducer looking toward the end of the freely floating armature and showing thcoverlapping pole pieces .of the permanent magnet.

Heretofore in the art it has been customary to utilize'. a telephone receiver unit with various modifications in loud speaker assembly. factory for the electrical reproduction of sound where the received energy does not exceed a particular amplitude. However, where 'the amplitude of the received energy is very large and the volume of the reproduced sound very considerable, the efiiciency of the telephone receiver unit becomes very l'ow. Under these circumstances the reproduced sound is not clear and there is a con- A telephone unit is quite satistinuous tendency for the diaphragm to rattie 'and reproduce extraneous noises. In other types of reproducers 'it has been proposed to interpose an armature between the sound reproducing diaphragm and the oper,-A

ating mechanism. The armature has normally been mounted'between pivots or fulcrumed in a given position or otherwise secured or connected to the framepof the reproduccr mechanism. These connections have inherently introduced mechanical inertia and friction.` In the reproduction of radio broadcast music or speech it is essential that the reproducing mechanism follow the energy variation with rapidity and ex'- treme accuracy. Mechanical 'inertial and friction often introduce such mechanical resistance that a positive force must be overcome by the minute incoming signaling energy before this relatively weak energy may actuate the sound reproducing diaphragm proper. By my. invention I eliminate this undesirable mechanicalinertia and friction by providing a true, freely floating armature connected with the sound reproducing diaphragm. I provide a permanent magnet having inwardly projecting pole pieces, each having flat faces directed toward each other in overlapping relationship, An electromagnet is provided between the inwardly projecting pole` pieces, the electromagnet having a hollow core so related to the pole faces as to permit an armature to be freely floating within the hollow core and between the overlapping pole faces. The armature is connected with the sound reproducer dia,- phragm and the incoming signal energy ap- The form of the electromagnetic reproducer illustrated in the drawings and hereinafter described in detail has been found to be one of the practical embodiments of the-invention and capa-bleef eflicientoperation and practical in manufacture and production. V

Referring now more 4particularly to the drawings, the electromagnetic reproducer is l5 shown vas comprising a circular casing 1 and 2,'the upper and lower sections of which are secured together by means of bolts 3. The uppersection 2 of the casing is screw thread; ed ate to receive a ferrule 'or other form of adapter in which an acoustic horn is mounted.. The sound reproducing diaphragm is mounted wfithiri the casing formed by sections 1 and 2. vIt will be understood Athat thesesections might be screw threaded, one

' 25 into the other with the diaphragm 5 seated between the sections 1 and 2 and that means4 other than the screws 3 as illustrated may be employed in securing the parts together.

The permanent magnet means employed inl the reproducer consists of a horseshoe magnet 16 having polesl 9 and 10 of opposite polarity. The magnet is suspended from the section 1 of the casing by means ofvbolts 7 and nuts 8 'which pass .through pole pieces 30 and 31. The pole piecesl 3() and 31 are thereby secured rigidly between the horseshoe magnet' and the lower surface 29 of the casing section 1. The pole pieces 30 and 31 project inwardly rtoward each other as 40 shown in Figure 2. Pole members 14: and 15 are secured onopposite sides of pole piece 30.4 The pole piece 31 is provided with pole members 16 and 17 secured on opposite sides thereof in a,l manner similar to the method of securing pole members 14and 15v on opposite sides of pole piece30. Each of the pole members, 14, 15, 16, and 17hasa corner cut out at the end thereof, the remaining portion of each pole member forming a fiat pole face adjacent each other and arranged in parallel" spaced relationship.

y 'That is to say pole member 14 is provided with a flat pole face 20, whilepole' member 15 has a flat pole face 18. The pole member 17 has aflat'pole face 19, while pole member 16 has a flat pole face 21. The pole members are so arranged that the pair of pole -faces of similar polarity are diagonally positionedwith respect tov the pole faces of the pair of pole members of opposite polarity. This will be understood when the end 9 of permanent magnet 6-is considered as north while thel opposite end 10 of the permanent `6 is considered to bev south. Pole 05 faces 21 and 19 in' Fig. 1'wil1 then be south electromagnet in such manner that the poles while pole faces 18 and 20l in Fig. 1

will be north poles. i

An electromagnet winding 24 is provided 4disposed between the extremities of pole pieces 30 and 31 and between the pole members 14, 15, 16, and 17 The magnet winding 24 is wound upon a hollow core, the opening of which is aligned with the parallel gap between the pole faces of the pole members. l/Vithin this hollow core and between the pole faces I -mount a true floating armature member 23. vThe armature 23 may be connected to the sound reproducing diaphragm 5 in a variety of different' ways. I have shown the armature 23 connected by means of downwardly depending links 25' and 26 passing through an aperture 22 in the lower Aportion of section 1 of thecasing, and rig-. idly connected to the diaphragm at spaced intervals as represented at 27 and 28. I may also mount the'armature 23 with respect to the diaphragm 5 by means of a depending Ul shaped strip connected to the'.

center. o-f the diaphragmy 5 andA straddling the electromagnetwinding 24 and thel pole members being secured to opposite 'ends of;-

the armature 23. l

It will be seen that the armature in my rer-1` I producer is a true freely floatingv device.`

There are .no frictionallcontacts or pivotstointroduce undesirable friction or mechani-v.

cal inertia. The signaling energy lead into the electromagnet winding 24 is utilized in'A the fullest degree to produce a pushpull effect on-the armature. No fulcrum points a positive air-gap left around the armature so that it is free -tovibrate in accordance with the incoming signaling energy.

The armature vibrates with substantially straight line movement in a direction substantially at right angles to the. axis of the enico are employed in mounting the. armature .but

tire amplitude of Vibrationthus develope@- may beimpressed directly upon thedia phragm. The effect of the electro-magnet mechanism is to operate the diaphragm by push-pull forces ina vertical' direction wit-h respect to the electromagnet. l While I have illustrated my' inventionv in' a certain preferred embodiment I desire that it be understood that modifications maybe made and that no limitations are intended uponthe invention-other than those imposed by the scopeof the appended claims.

What I claim and desire to secure by Letrack `in said casing, an armature arranged to freely float within said-hollow core and eX- tending between said pole pieces and connections between extremities of said armature and said diaphragm for imparting movement to said diaphragm. l

2. electromagnetic sound reproducer comprising in combination acasing, permanent magnetic means, electromagnetic means located between said permanent magnetic means, a freely floating armature positioned within both of said means, a diaphragm in said casing and aconnection between opposite ends of said freely lioating armature and said diaphragm whereby vibrations transverse to the axis of said electromagnetic means may be imparted to said diaphragm.

3. An electromagnetic sound reproducer, comprising in combination a casing, a permanent magnet, Ia plurality of pairs of pole pieces secured to said magnet each pair of said pole pieces having flat faces projecting toward each other in overlapping relationship, an open cored electromagnet positioned between said pole pieces, a diaphragm carried by said casing and a freely ioating arkmature interposed within said electromagnet and between said pole pieces and connected at its opposite ends with said diaphragm whereby substantially straight line motion transverse to the axis of said electromagnet is imparted to said armature for actuating said diaphragm.

4. An electromagnetic sound reproducer comprising in combination a casing, a permanent horseshoe magnet, a pole piece secured to the extremity ofeach side of said horseshoe magnet, a pair of pole members att-ached tofeachof said pole pieces, each of said pole members having a corner cut out of the end thereof with the remaining por` tion of the pole members forming .pole faces adjacent each other, an electromagneticl mechanism having a' hollow core, a diaphragm carried 1n said casing and an armature freely ioating within said hollow core and between said pole faces and connected at its opposite extremities with said diaphragm, whereby substantially straight line vibration perpendicular to the axis of said electromagnetic mechanism is imparted to said armature for driving said diaphragm.

5. An electromagnetic sound 'reproducer comprising in combination a casing, a permanent horseshoe magnet, a'pole piece secured to the extremity of each side of said h orseshoe magnet, a pair of pole members at tached to eac of said pole pieces, each pair of said pole members having pole faces offset one with respect to the other, with the oflset portion of one pole member on one of said pole pieces diagonally positioned with respect to the corresponding offset portion of an opposite pole member on the other of said pole pieces, said offset portions providing substantially parallel faces, an elec tromagnet having a hollow core disposed between said pole pieces, af sound reproducing diaphragm and a true floating armature 'positioned within said hollow core and between said parallel faces and connected at its op posits ends with said diaphragm whereby substantially straight line vibration is imparted to said armature in a direction substantially transverse to the axis of said electromagnet for driving said diaphragm.

tremities thereof, a reely floating armature positioned lwithin said air gap, means for creating a variable magnetic lield transverse to the axis of said armature, a diaphragm carried'in said casing and a connection between opposite ends of said freely floating armature and said diaphragm whereby vibrations transverse to the axis of said armature may be imparted to said diaphragm in accordance with the variations of said magnetic field,

orion. E. BRIGHAM.

6. An electromagnetic sound reproducen 

